Common Core addition and subtraction strategies explained for parents: open number lines, partial sums, counting up to subtract, and when the standard algorithm is taught.
Under the Common Core, children add and subtract using strategies based on place value before they learn the standard algorithm (the "carrying and borrowing" method many parents learned). They use drawings, number lines and breaking numbers into tens and ones in 1st and 2nd grade (1.NBT.C.4, 2.NBT.B.7).
The standard algorithm is expected by 4th grade: "Fluently add and subtract multi-digit whole numbers using the standard algorithm" (4.NBT.B.4). The strategies don't replace it; they explain why it works.
Partial sums: 47 + 38
Counting up on an open number line: 62 − 27
The standard algorithm, for comparison: 47 + 38
Ask your child to solve one problem two ways (number line and tens-and-ones) and explain which was quicker.
Pretend you spend 63 cents. Count up to a dollar together: 63 to 70 is 7, 70 to 100 is 30, so 37 cents change.
Before solving 47 + 38, guess: about 50 + 40 = 90. Is the answer near that?
Methods and tests vary by state and district; your child's teacher is the best guide to what their class uses. Last checked October 2026.
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